The invention relates to a high pressure transfer device especially adapted for use at very high pressure differentials (e.g. 50 to 100 bars), such are encountered when pumping up hard particulate material (such as manganese nodules) from an ocean floor (e.g. 15,000 feet below sea level) to the surface, and a method for utilizing such a device for continuously conveying such hard particulate material under such circumstances.
Conventional high pressure transfer devices, such as shown in U.S. Pat. No. 4,082,368 (the disclosure of which is hereby incorporated by reference herein) perform very well at most relatively small pressure differentials. For instance, at pressure differences of 8 to 20 bars, which are conventionally encountered when such devices are used in conjunction with pulp digesters, little problems result. Nor do many problems result at pressures conventionally encountered conveying coal, oil shale, mineral ores, etcetera from the face to the surface of underground mines as provided in U.S. Pat. No. 4,082,368. However when utilized at extremely high pressure differentials (e.g. 50 to 100 bars) such as are encountered in pumping manganese nodules and like hard particulate material from the ocean floor to the surface, the housing for the high pressure transfer device has a tendency to deflect outwardly, resulting in unacceptable leak volume so that the device cannot adequately perform its intended function. Such outward deflection also results in inward deflection of other portions of the housing, which may actually cause binding of the rotor.
Attempts to "beef up" the construction of the housing to prevent deflection, or to otherwise compensate for the deflection, have not been successful. The deflection problem is compounded by the fact that the differential pressure may be 100 bars when a column of nodules is being conveyed to the surface, but just 10 to 20 bars when the feeder is idling.
According to the present invention, a high pressure transfer device, and method of utilization thereof to transport hard particulate material under very high pressure conditions, are provided which overcomes the deflection problem inherent in prior art high pressure transfer devices.
The apparatus according to the present invention includes the conventional components of: A pocketed rotor containing a pair of diametrically through-going pockets perpendicular to each other with the housing enclosing the rotor. The housing has an exterior periphery and has four ports disposed around the periphery for registry with inlets to and outlets from the pockets. Means are provided for rotating the rotor in the housing with respect to the ports about a given axis of rotation, and screen means are associated with the device for screening particulate material above the predetermined size out of the liquid passing through at least one of the ports. In order to prevent deflection of the housing, according to the present invention means are provided for applying a radially inwardly directed force to the housing exterior periphery roughly proportional to a force tending to deflect the housing radially outwardly, so that significant deflection of the housing is prevented. Thus, the device may operate at high pressure with an acceptably low level of leakage to convey hard particulate material under high pressure, yet will adjust to widely varying pressure conditions (e.g. 10 bars to 100 bars).
The means for applying a force to the housing preferably comprises means for applying a force proportional to a pressure of the liquid entering the high pressure inlet port of the housing. One form that the structure can take is a jacket comprising first and second jacket portions operatively engaging a central belt portion of the housing on opposite sides thereof. At least one pressure responsive force applicator (such as a piston and cylinder arrangement, or bellows arrangement) is associated with the first jacket portion, and force transmitting means (such as a pair of rods) interconnect the jacket portions so that the force applicator structure applies a force to both the jacket portions tending to bias the jacket portions toward each other (although no actual relative movement takes place).
In practicing the method of the invention for continuously conveying hard particulate material under high pressure the liquid containing the hard particulate material is fed into a first of the housing ports for entry into a through-going pocket of the rotor. The rotor is rotated in its given direction of rotation so that it progressively rotates past each of the housing ports while withdrawal of liquid introduced through the first port is provided through a third port, opposite the first port while screening of the particulate material above a predetermined size out of the liquid passing through the third port takes place. Liquid under high pressure is pumped toward the rotor through a fourth port of the housing located before the first port in the direction of rotation of the rotor, and between the first and third ports, while withdrawal of the liquid with entrained hard particulate material from a through-going pocket takes place through a second port, located opposite the fourth port. A radially inwardly directed force is applied to the housing exterior periphery roughly proportional to a force tending to deflect the housing radially outwardly adjacent the second and fourth ports so that significant deflection of the housing is prevented, the radially inwardly directed force preferably being proportional to the pressure of the liquid entering the housing fourth port. The high pressure transfer device is preferably mounted deeply underwater and disposed so that the axis of rotation of the rotor is substantially vertical. The method is practiced to transport hard particulate material under high pressure even from an ocean bottom at, for example, 15,000 feet, with a pressure difference of about 50 to 100 bars.
It is the primary object of the present invention to provide a high pressure transfer device, and method of conveying hard particulate material (such as from an ocean bottom) utilizing the high pressure transfer device, so that the device will successfully operate at very high pressure differentials, as well as at relatively low idling pressure differentials. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.